The present invention relates to machine tools in general, and more particularly to improvements in supports which can be used in machine tools to engage portions of workpieces during treatment at a material removing station. Still more particularly, the invention relates to improvements in tailstocks which can be used with advantage in so-called universal grinding machines wherein an indexible head carries several spindles each of which can support and transmit torque to a discrete grinding wheel or to a cluster of two or more coaxial grinding wheels.
Universal grinding machines are designed to remove material from different types of workpieces without any exchange of tools. Thus, one of the grinding wheels can be used to remove material from external cylindrical surfaces, another grinding wheel can be used to remove material from internal cylindrical surfaces, and a third grinding wheel can be used to remove material from flat or substantially flat surfaces. The machines are designed in such a way that the idle grinding wheels can remain on their spindles while a selected grinding wheel treats a workpiece at the material removing station. The head is normally indexible to a number of different positions, at least one for each of its spindles, so that it can move a selected grinding wheel to the operative position. Those parts of the grinding machine which are located in the path of movement of the head during indexing of a selected spindle and of its grinding wheel to or from the material removing station must be moved out of the way or detached from the machine. This entails extensive periods of idleness of the machine. For example, if a workpiece is held between the centers of a headstock and a tailstock during removal of material from its external surface, the headstock as well as the tailstock must be located close to the material removing station in order to ensure adequate retention of the workpiece between the respective centers. However, such supports for the workpiece are at least likely to prevent indexing of the grinding wheel which is to be used or which was used for removal of material from the external surface of the workpiece between the two centers. Therefore, at least one of these supports (i.e., the headstock or the tailstock) must be detached from the frame of the universal grinding machine or it must be shifted, in its entirety, to a position sufficiently remote from the material removing station to allow for indexing of the head and of the spindles and grinding wheels thereon. Thus, it is necessary to detach at least one of the supports or it is necessary to enlarge the frame of the universal grinding machine so as to provide room for a shifting of the headstock and/or tailstock to a position in which the thus shifted support is sufficiently remote from the material removing station for unimpeded indexing of the head. Neither of these solutions is satisfactory. Furthermore, it is necessary to dismantle the tailstock or to move it out of the way if a workpiece which was held between the centers of the headstock and the tailstock is to be followed by a workpiece which is to be held and rotated by the headstock alone, e.g., in order to enable a grinding wheel to remove material from the surface surrounding an axial bore in one end face of the workpiece.